Effect of Palm-Based Soap Noodles Concentration on Dust Explosion Severity in a Spherical Vessel

(1)

Effect of palm-based soap noodles dust concentration on dust explosion severity in a spherical vessel

M.S.R Mazilan, S.Z Sulaiman

^⇑

, A.H Sofian, S.K. Abdul Mudalip, R. Che Man, Z.I.M. Arshad, S.M. Shaarani

Faculty of Chemical and Process Engineering Technology, Universiti Malaysia Pahang, 26300 Gambang, Pahang, Malaysia

a r t i c l e i n f o

Article history:

Available online xxxx

Keywords:

Agglomeration Explosion Deflagration index Dust

Propagation

a b s t r a c t

The dust explosion propagation of palm-based soap noodles was experimentally studied in a 20-L spherical vessel. Understanding the effect of concentration on this metric is a prerequisite to characterizing the severity of the explosion. This study focused on the link between concentration and overpressure (Pmax), rate of pressure rise (dP/dt), and deflagration index (KST). The highest Pmax, dP/dt, and KSTwere recorded at 400 g/m³, corresponding to a class St-2 dust with a strong explosion. The agglomeration process evi- dently controlled the mass burning rate, which affected the dust explosion propagation. This data can help design preventive measures related to palm-based soap noodle dust explosions.

Selection and peer-review under responsibility of the scientific committee of the 6th International Con- ference of Chemical Engineering & Industrial Biotechnology (ICCEIB 2022).

1. Introduction

Dust explosions have caused massive losses and damage to peo- ple, property, and the environment. In agriculture and other related industries, processing produces over 70% of the total combustible dust[1], which can occasionally lead to fire and explosion incidents. According to statistics from the Department of Safety and Health of Malaysia (DOSH), dust explosion accidents are on an upward trend. These accidents cause fatalities, significant casu- alties, and property damage[2]. An extensive analysis of the factors contributing to dust explosions and their propagation mechanisms is essential for designing effective preventive measures. The severity of a dust explosion can be characterized by its maximum overpressure (Pmax), rate of pressure rise (dP/dt), and deflagration index (KST). The dust explosion characteristic is sub- ject to the natural behavior and reactivity of the dust [3]. For instance, tea dust is less reactive than low-density polyethylene (LDPE) dust. A tea dust explosion recorded a Pmaxof 2.09 bar and KSTof 190.31 bar-m/s[4], corresponding to a class St-1 weak- to medium-level explosion [4]. An LDPE dust recorded a violent explosion with a Pmaxof 14 bar, corresponding to a class St-2[5].

Besides dust reactivity, previous research demonstrated that several factors control dust explosions, including dust particle size [6,7], concentration[8,9], and agglomeration[10–12]. Smaller par-

ticles are easier to ignite and have a higher mass burning rate[6,7], given their larger surface area. Wan Sulaiman et al. studied the effect of rice flour concentration on explosion severity, while Todaka et al.[9]explored the influence of jatropha and spent coffee dust on maximum overpressure. They concluded that maximum overpressure increased alongside concentration, up to the rich mixture condition, at which point the lack of air in the dust cloud decelerated burning and moderated the maximum overpressure.

Todaka et al.[9]also reported that dust reactivity played a major role in classifying the severity of an explosion. Dispersion is one of the elements needed to initiate a dust explosion since it allows the dust to mix with the oxygen-containing air. If the dust tends to agglomerate, dispersion becomes difficult, which could hamper explosion propagation[10].

Soap noodle (or glycerol) is made from vegetable or animal fats by the saponification reaction process[13]. Soap noodle is a small noodle-alike substance that is the primary ingredient in the pro- duction of soap bars. Palm oil is commonly used to make soap noodles [13]. To date, there are a lot of industries producing soap noodles. It can be said that a lot of dust is generated during the processing step, which will trigger the dust explosion hazard. At pre- sent, no data on dust explosions from palm-based soap noodles has been reported.

Studies have shown that particle size, concentration, and agglomeration significantly impact explosion severity. The pub- lished explosion characterization data was based on agricultural, food-based, and polymer-based dust. Gathering and analyzing

https://doi.org/10.1016/j.matpr.2023.04.589

Selection and peer-review under responsibility of the scientific committee of the 6th International Conference of Chemical Engineering & Industrial Biotechnology (ICCEIB 2022).

⇑Corresponding author.

E-mail address:[email protected](S.Z Sulaiman).

Contents lists available atScienceDirect

Materials Today: Proceedings

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / m a t p r

Please cite this article as: M.S.R Mazilan, S.Z Sulaiman, A.H Sofian et al., Effect of palm-based soap noodles dust concentration on dust explosion severity in a spherical vessel, Materials Today: Proceedings,https://doi.org/10.1016/j.matpr.2023.04.589

(2)

palm-based soap noodle dust explosion data helps the industry design safety preventive measures, since this dust is produced throughout the soap manufacturing process. This study examined the effect of palm-based soap noodle concentration on explosion severity. The characterization was based on Pmax, dP/dt, and KST. In addition, the mechanism of explosion propagation was analyzed at each concentration.

2. Methodology

2.1. Materials and sample preparation

The material employed in this study was obtained from a local company that produces palm-based soap noodles. The soap noodle was ground and sieved into dust by a high-performance laboratory grinder. Due to grinder limitations, the particle size was set to 210

l

m, which is in the range of explodable dust size[11].

2.2. Dust explosion testing

The palm-based soap dust was combusted in a Siwek 20-L spherical vessel, as shown in Fig. 1. The vessel was constructed from stainless steel and was pressure-rated at 20-bar. It incorpo- rated a 0.6-L dust container, pressure sensors, a dispersion system, two chemical ignitors (as an ignition system), and a control system.

The overpressure was measured using two pieces of ‘‘Kistler”

piezoelectric pressure sensors installed in the vessel. The explosion test rig was manufactured by Adolf Kuhner and the experimental procedure was based on ASTM E1226[14]. The dust was loaded into the 0.6-L dust container. It was dispersed using compressed air, then immediately ignited by the chemical ignitor. The ignition delay time, tv, was fixed at 60 ms. The 20-L spherical vessel was also integrated with a KSEP control system, which controlled the dispersion and ignition and was part of the data logger. The explosion test was repeated thrice with variances in the reading of less than ± 5 % at each run.

2.3. Chemical properties Identification: Analysis by thermogravimetry (TGA) and scanning electron microscope (SEM)

The moisture and ash contents of the material before and after the explosion test were analyzed via thermogravimetric analysis

(TGA). A 5 mg sample was heated to 900°C at a ramping rate of 10°C per minute[4]. The moisture and ash contents were calculated based on mass loss and the differential loss using the equation stated below[4]:-

%of Moisture ¼ ðWW105Þ=W x 100% ð1Þ

%of Ash¼ ðW600W105Þ=W x 100% ð2Þ Where W is the initial mass of the sample (mg), W105 and W600 are the mass loss at 105°C and 600°C, respectively. In addition, the surface morphology of the dust particles was observed using a scanning electron microscope (SEM) model FEI-Quanta 450.

3. Result and discussion

3.1. Explosion propagation at various concentrations of palm-based soap dust

The overpressures, Pmax, of palm-based soap explosions at various concentrations were measured over time, as shown inFig. 2.

Based on the pressure development profile, the palm-based soap dust explosion propagated in three phases: incipient, growth, and full development[15]. The incipient phase, which occurred in the first 160 ms, indicated a slow combustion process. It was suspected that the palm-based soap dust’s stacked and irregular shape (Fig. 2) made them agglomerate easily and difficult to disperse. This slowed the dispersion and ignition of the dust during the first 160 ms. Once the dust had ignited, combustion was sustained, and the flame started to propagate, leading to the next phase, growth. In this phase, the overpressure climbed steeply up to a point, after which the pressure leveled off, and the explosion was said to be fully developed. The highest overpressure was recorded at each concentration. It was suspected that the continuous mass burning caused the flame to accelerate and resulted in an increase in overpressure.Fig. 2also depicts that the explosion propagation phase was comparable for all concentrations with various buildup overpressure.

The palm-based soap dust burnt the slowest at the concentration of 150 g/m³, taking about 400 ms to complete the explosion.

It is suspected the material was less reactive at this low concentration, which slowed down the mass burning rate, moderated the explosion process, and reduced the overpressure buildup. The ignition onset varied independently of the soap dust concentration.

This peculiar observation was suspected to be due to the hydrophi- lic properties[16].

3.2. Effect of dust concentration on maximum explosion overpressure (Pmax) and rate of pressure rise (dp/dt)

The severity of dust explosion can be observed via the maximum overpressure, Pmax, and the rate of pressure rise, dP/dt. The Pmaxand dP/dt trends at various palm-based soap dust concentrations are presented inFig. 3. The higher the dust concentration, the higher the Pmax and dP/dt until it reaches a rich concentration.

Fig. 3also shows that raising the concentration from 300 g/m³to 400 g/m³ increased Pmax by 48% from 10.2 bar to 15 bar. At 300 g/m³, the dust may have agglomerated more and was more difficult to disperse. This would have reduced the particle surface area and slowed down the mass burning rate. The morphology image (Fig. 4) depicted that unreacted dust particles were more prevalent at 300 g/m³than at 400 g/m³. Likewise, the ash (combustion product) and moisture contents were much lower at 300 g/m³, indicating that less water was produced during the combustion due to the low mass burning rate. This mechanism could explain Fig. 1.Schematic diagram of Siwek 20 L spherical vessel.

(3)

0 3 6 9 12 15

0 100 200 300 400 500

Overpressure, bar

me, ms

150 g/m³ 200 g/m³ 300 g/m³ 400 g/m³ 500 g/m³ 900 g/m³ 1000 g/m³

0.00 0.10 0.20 0.30 0.40 0.50

100 200 300

stacking & irregular shape Incipient

phase

Growth to explosion

Fig. 2.Explosion propagation at different concentrations of palm-based soap dust.

0 50 100 150 200 250 300 350 400

0 2 4 6 8 10 12 14 16 18

0 200 400 600 800 1000 1200

dp/dt, bar/s

ra b , xa m P ,e r us se r pr e v O m u mi xa M

Concentration, kg/m

³

Pmax dP/dt

Fig. 3.Maximum Overpressure and rate of pressure rise as a function of palm-based soap dust concentration.

Unreacted dust

Unreacted dust Unreacted dust

(A) (B) (C)

Fig. 4.Morphology of soap dust after explosion. (A) at 300 g/m³. (B) at 400 g/m³. (C) at 500 g/m^3.

(4)

the significant difference in Pmax when the concentration was raised from 300 g/m³to 400 g/m³. However, further increase in the concentration does not affect Pmax. It is postulated that any concentration above 400 g/m³is a rich concentration. At this condition, there is not enough oxygen in the dust cloud to sustain the explosion propagation, thus affecting the P_maxdevelopment.

Fig. 3also shows that the rate of pressure rise is comparable with the Pmaxtrend. Likewise, Pmax, the highest dP/dt was also recorded at 400 g/m³. As expected, the degree of agglomeration was lower and the dust cloud was easier to disperse at this point.

The mass burning rate also increased rapidly and caused the dP/dt to rise significantly at 400 g/m³. The evidence showed that the critical concentration of palm-based soap dust was 400 g/m³, where it could cause catastrophic dust explosions.

3.3. Deflagration index KSTat various Palm-Based soap dust concentration

The deflagration index, K_STwas used to classify the severity of the dust explosion in a closed system. It can be calculated using the cubic’s law equation[14]as stated below:

KST¼ ðdP=dtÞmax:V¹⁼³ ð3Þ

Where dP/dt is the rate of pressure rise and V is the volume, in m³ of the testing chamber. The chamber volume is calculated based on V = 4/3

p

^r³, where r is radius in unit meter. Based on the vessel specification, the radius is 0.41 m giving the volume is 0.29 m³respectively.

As indicated inFig. 3, the three-point concentrations at 150 g/

m³, 400 g/m³, and 900 g/m³were used to evaluate KSTand measure the severity of the palm-based soap dust explosion. FromTable 1, the highest KSTof 242.3 bar-m/s was obtained at a concentration of 400 g/m³. The KSTwas higher than 200 bar-m/s, placing it in class St-2, which is associated with a strong explosion[17]. This is con- sistent with the Pmaxand dp/dt results, implying that the palm- based soap dust was critical at 400 g/m³. Beyond the concentration, palm-based soap dust tended to create a weak to moderate explosion due to the KSTvalue being below 200 bar-m/s.

4. Conclusions

The severity of palm-based soap dust explosion was experimentally analyzed in a 20-L explosion chamber. A severity characterization was observed based on the maximum overpressure, rate of pressure rise, and deflagration index as a function of concentration. Results showed that the net mass burning rate was controlled by the degree of agglomeration and how it affected the explosion.

The degree of agglomeration varied with concentration, proving that the concentration of palm-based soap dust had a significant effect on the severity of dust explosions. The highest Pmax of 16 bar, dP/dt of 366 bar/s, and KSTof 242.3 bar-m/s were recorded at the concentration of 400 g/m³. The K_STexceeded 200 bar-m/s, indicating that a severe explosion could happen at a palm-based soap dust concentration of 400 g/m³. The data attained from this analysis can serve as preliminary safety information for designing preventive measures against palm-based soap dust explosions.

CRediT authorship contribution statement

S.Z. Sulaiman: Conceptualization, Methodology. M.S.R. Mazi- lan:Writing – original draft.A.H. Sofian:Data curation.S.K. Abdul Mudalip:Visualization, Investigation.R. Che Man:Supervision.Z.I.

M. Arshad:.S.M. Shaarani:. Data availability

Data will be made available on request.

Declaration of Competing Interest

The authors declare that they have no known competing finan- cial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors would like to thank Universiti Malaysia Pahang for financially supporting this study under UMP grant RDU192325. We also would like to acknowledge the Faculty of Chemical and Pro- cess Engineering Technology, University Malaysia Pahang, for the research facilities.

References

[1] W. Wu, W. Huang, A. Wei, M. Schmidt, U. Krause, D. Wu, Inhibition effect of N2/CO2 blends on the minimum explosion concentration of agriculture and coal dusts, Powder Technology 399 (2022), https://doi.org/10.1016/j.

powtec.2022.117195.

[2] B. Tan, Z. Shao, B. Xu, H. Wei, T. Wang, Analysis of explosion pressure and residual gas characteristics of micro-nano coal dust in confined space, Journal of Loss Prevention in the Process Industries 64 (2020),https://doi.org/10.1016/

j.jlp.2020.104056.

[3] W. Kowhakul, H. Shibahara, H. Masamoto, M. Shigematsu, Dust explosion characteristics of cellulose ethers and cellulose acetates with various degrees of acetylation, Journal of Loss Prevention in the Process Industries 44 (2016) 544–550,https://doi.org/10.1016/j.jlp.2016.07.018.

[4] S.Z. Zubaidah, N.H. Semawi, N.S. Ahmad Mutamin, S.K. Abdul Mudalip, R. Che Man, S. Md Shaarani, Z.I. Mohd Arshad, H. A Abdul Bari, R. Md Kasmani, Preliminary study on the tea dust explosion : The effect of tea dust size. MATEC Web Conference 2019. 255:7. 10.1051/matecconf/201925502014

[5] H. Badli, M.N. Aridin, S.Z. Sulaiman, J. Susaidevas, N.A. Mahamad, K. Nizar, Assessment on the severity of low density polyetylene (LDPE)/Ethylene hybrid explosion, IOP Conference Series: Materials Science and Engineering 702 (2019),https://doi.org/10.1088/1757-899X/702/1/012050.

[6] H. Zhang, X. Chen, Y. Zhang, Y. Niu, B. Yuan, H. Dai, S. He, Effects of particle size on flame structures through corn starch dust explosions, Journal of Loss Prevention in the Process Industries 50 (2017) 7–14,https://doi.org/10.1016/j.

jlp.2017.09.002.

[7] M. Pietraccini, E. Danzi, L. Marmo, A. Addo, P. Amyotte, Effect of particle size distribution, drying and milling technique on explosibility behavior of olive pomace waste, Journal of Loss Prevention in the Process Industries 71 (2021), https://doi.org/10.1016/j.jlp.2021.104423.

[8] WZ Wan Sulaiman, MF Mohd Idris, J Gimbun, SZ Sulaiman, Assessment of explosibility and explosion severity of rice flour at different concentration and ignition time, Proc Safety Prog 39 (2020). https://doi.org/10.1002/prs.12107.

[9] M. Todaka, W. Kowhakul, H. Masamoto, M. Shigematsu, Thermal analysis and dust explosion characteristics of spent coffee grounds and jatropha,Journal of Loss Prevention in the ProcessIndustries 44 (2016) 538–543,https://doi.org/

10.1016/j.jlp.2016.08.008.

[10] P. Bagaria, J. Zhang, E. Yang, A. Dastidar, C. Mashuga, Effect of dust dispersion on particle integrity and explosion hazards, Journal of Loss Prevention in the Process Industries 44 (2016) 424–432, https://doi.org/10.1016/j.

jlp.2016.11.001.

Table 1

KSTat different concentrations of palm-based soap dust.

Concentration, g/m³ Ash Moisture content (%) Pmax

(bar)

dP/dt (bar/s)

KST

(bar-m/s)

Testing Vessel volume m³

150 2.99 9.5 104 68.83

0.29

400 7.46 16.0 366 242.3

900 5.98 15.1 282 186.7

(5)

[11] O. Kalejaiye, P.R. Amyotte, M.J. Pegg, K.L. Cashdollar, Effectiveness of dust dispersion in the 20-L Siwek chamber, Journal of Loss Prevention in the Process Industries 23 (1) (2010) 46–59, https://doi.org/10.1016/j.

jlp.2009.05.008.

[12] Z. Luo, L. Liu, F. Cheng, T. Wang, B. Su, J. Zang, S. Gao, C. Wang, Effects of a carbon monoxide-dominant gas mixture on the explosion and flame propagation behaviors of methane in air, Journal of Loss Prevention in the Process Industries 58 (2019) 8–16,https://doi.org/10.1016/j.jlp.2019.

01.004.

[13] S.K. Yeong, Z. Idris, H.A. Hassan, Palm Oleochemicals in Non-food Applications.

AOCS Press2012. Palm Oil: 587-624 10.1016/B978-0-9818936-9-3.50023-X.

[14] M. Hertzberg, K.L. Cashdollar, I.A. Zlochower, G.M. Green, Explosives dust cloud combustion. Symposium (International) on Combustion 1992. 24 (1):1837-1843. 10.1016/S0082-0784(06)80215-8.

[15] H Badli et al 2020 IOP Conf. Ser.: Mater. Sci. Eng.991012119DOI 10.1088/

1757-899X/991/1/012119

[16] A. Kuntom, H. Kifli, Properties of soaps derived from distilled palm stearin and palm kernel fatty acids, J Surfact Deterg 1 (1998) 329–334.https://doi.org/10.

1007/s11743-998-0032-4.

[17] OSHA. Hazard Communication Guidance for Combustible Dusts., in U.S.

Department of Labor <osha.gov/Publications/3371combustible-dust.pdf>, U.S.

D.o. Labor, Editor.